You should have experience with Excel before trying to use formulas to calculate what day of the week the 15th of a given month is, and you have several options to do this.

Q. Is there an easy way to calculate how long in years and months the employees have been working for my company? A. Excel can do that, as long as you’ve listed all the employees in a database. If so, ...

The article How to calculate conditional subtotals in an Excel revenue sheet uses simple expressions, a function, and a conditional format to display a daily balance in a revenue sheet.